Structure of atom
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This document discusses the particulate nature of matter. It explains that matter is made up of particles including atoms, molecules, and ions. Atoms are the smallest particle of an element, molecules contain two or more bonded atoms, and ions are charged particles formed in liquids or molten states. The document then discusses the kinetic theory of matter and how particle behavior differs between solids, liquids, and gases. It also summarizes the early models of the atomic structure proposed by scientists like Dalton, Thomson, Rutherford, and Bohr. Finally, it defines key atomic concepts like protons, neutrons, isotopes, and their uses.
Structure of atom
- 2. Particulate Nature of Matter Matter- anything that has mass and occupies space Particle + particle = matter Iron (Fe) from iron atom NaCl from sodium ions and chloride ion H2O from water molecules
- 3. Atoms an atom is the smallest particle of an element example : “O” for oxygen atom Molecules contains two or more atoms which are bonded together ( maybe same element or not ) example : H2 and CCl4 Ions -ions are charged either positive or negative -are form in liquid or molten state -lose electron (+ ion),gain electron (- ion) example : Na+ , Mg2+ , Br-
- 4. Kinetic Theory of Matter Solids - strong forces of attraction - particle only vibrate (fixed shape and volume) Liquids - force of attraction weak than solid - particle can move around (follow container shape) Gases - no attraction between particles - particle move faster and freely (zigzag)
- 6. Diffusion - example : perfume - light and small particle diffuse faster - heavy and large particle diffuse slow
- 8. The Atomic Structure Democritus Democritus proposed that if a piece of gold cut into smaller until cannot cut anymore, called atom. John Dalton (1766-1844) J.J.Thomson (1856-1940) Ernest Rutherford (1871-1937) Neils Bohr (1885-1962) James Chadwick (1891-1974) - - - - -
- 9. John Dalton(1766-1844) In 1808, he proposed : 1. All matter is composed of atoms. 2.Atoms cannot be created or destroyed. 3. All the atoms of an element are identical. 4.The atoms of different elements are different. 5.When chemical reactions take place, atoms of different elements join together to form compounds.
- 10. J.J.Thomson (1856-1940) 1. It was the first model of the atom. 2. 1897- Thomson discovered the electron (negatively- charged). 3. Thomson suggested that an atom is a positively- charged sphere with electrons embedded in it like a raisin pudding.
- 11. Ernest Rutherford (1871-1937) 1. 1914- Rutherford discovered the proton 2. Rutherford model was based on the alpha particle scattering experiment 3. He proposed 1) all the positive charge of an atom is concentrated in the nucleus 2) an atom consists of a positively-charged nucleus with a cloud of electrons surrounding the nucleus
- 12. Neils Bohr (1885-1962) He was a student of Rutherford He proposed 1) electrons are arranged in orbits (electron shells) around the nucleus of the atom 2) electrons in a particular path have a fixed energy. To move from one orbit to another, an electron must gain or lose the right amount of energy
- 13. James Chadwick (1891-1974) He proposed that the nucleus of the atom contains proton and neutron and the nucleus is surrounded by a cloud of electrons
- 14. Atomic structure of an atom Atoms are made of three different types of subatomic particles called protons, neutrons and electrons Protons and neutrons are found in the nucleus and they are known as nucleons Nucleus is positively charged because the protons are positively charged and the neutrons are electrically neutral Electrons rotate around the nucleus in a certain orbit called shells, just like planets rotate around the sun SUBATOMIC PARTICLES + + proton neutron shell electron {nucleon
- 15. THE PROPERTIES OF SUBATOMIC PARTICLES Subatomic particles Proton Neutron Electron Symbol p n e¯ Relative electric charge +1 0 -1 Relative mass 1 1 _1__ 1840 An atom is neutral when it has the same number of protons and electrons
- 16. PROTON NUMBER The number of protons in an atom of an element Proton number = number of protons
- 17. NUCLEON NUMBER The sum of protons and neutrons in an atom element Nucleon number = number of protons + number of neutrons
- 18. The number of protons, electrons and neutrons in a particular atom are given in the Periodic Table by the nucleon number and proton number A : proton number Z :nucleon number X: symbol of an element The number of protons, electrons and neutrons can be determined from the nucleon number and proton number A X Z
- 19. Example: (a) Aluminium The symbol of the element above shows that it is aluminium Nucleon number = 27 Proton number = 13 Number of neutron = Aluminium atom has 13 protons, 13 electrons and 14 neutrons 27 Al 13 27 – 13= 14
- 20. Symbol of elements Most symbols are taken from the English name Element Symbol Hydrogen Carbon Nitrogen Boron H C N B
- 21. Some symbol are made up of two letters Some symbols are based on the Latin or Greek name Zinc Zn Aluminium Al Calcium Ca silicon Si Silver Ag Copper Cu Iron Fe Gold Au
- 22. Isotopes and their importance Are atoms of the same element with the same proton no. but different nucleon no. or neutron no. Isotopes of an element have same chemical properties but different physical properties Example: H1 H2 H3 , P31 P32
- 23. Uses of isotopes Medicine -Cobalt-60 is a radioactive isotope of cobalt. It decays by giving out gamma radiation. In radiotherapy, maglinant cancer cells are killed by directing a beam of gamma rays towards cancer cells Agriculture -radiation from radioisotopes is used to sterilise pests such as insects that destroy crops. -Fosforus 32 use as fertiliser. Industry -Gamma radiation is used to detect whether canned food or bottled drink is completely or partially filled